Traditional lighting technologies, such as incandescent bulbs and fluorescent bulbs, suffer from several drawbacks. For example, these lighting technologies do not have long lifespans or high energy efficiencies. Moreover, these lighting technologies are only offered in a limited selection of colors, and the light output by these lighting technologies generally changes over time as the source ages and begins to degrade. Consequently, light-emitting diodes (LEDs) have become an attractive option for many applications.
Many electronic devices include one or more image sensors for capturing images of the surrounding environment, such as a rear-facing camera or a front-facing camera. Each of these cameras is typically accompanied by at least one illuminant capable of providing robust luminosity across a wide field of view (FOV). Yet these illuminants are typically deficient in several respects.
For instance, LEDs embedded within electronic devices are often designed to produce a fixed white light with no tunable range. White light could be produced by combining a short-wavelength LED (e.g., one designed to produce blue light or ultraviolet light) and a yellow phosphor coating. Blue/ultraviolet photons generated by the short-wavelength LED will either travel through the phosphor layer without alteration or be converted into yellow photons in the phosphor layer. The combination of blue/ultraviolet photons and yellow photons produces white light (also referred to as “phosphor white light”). As another example, white light could be produced by a xenon flashlamp designed to produce extremely intense white light (also referred to as “xenon white light”) for short durations.
When an image is captured by an electronic device under phosphor white light or xenon white light, the effect is roughly equivalent to capturing the image under a fluorescent light source. Thus, phosphor white light and xenon white light will not provide an accurately reflected color spectrum, nor will they have any vibrancy. Instead, these illuminants simply flood the ambient environment with white light so that objects can be readily identified within images.
Recent development has focused on developing light sources that include two illuminants corresponding to different correlated color temperatures (CCTs). While these light sources may be able to produce a mixed white light that more accurately matches the color of an ambient environment, they can further take away from the color quality. For example, when mixed white light drops below the Planckian locus (also referred to as the “black body locus”) it may become pinkish in tone. Consequently, significant post-processing may be necessary to artificially recreate the original lighting of the ambient environment.
The drawings depict various embodiments for the purpose of illustration only. Those skilled in the art will recognize that alternative embodiments may be employed without departing from the principles of the technology. Accordingly, while specific embodiments are shown in the drawings, the technology is amenable to various modifications.